1. Field of the Invention
The present invention relates to a gas generator for generating a high pressure gas for expanding an air bag in an air bag system mounted in a vehicle or the like, and particularly, to a gas generator of the type which uses both of a compressed gas previously charged and a combustion gas generated from a combustible substance, in combination.
2. Description of the Prior Art
Conventionally, there has commonly been used a common type of a gas generator for an air bag system, which contains a pellet-shaped or grain-shaped gas-generating agent filled in a cylindrical casing. With such gas generator, the gas-generating agent is ignited and fired by an electrical or mechanical igniting device on the basis of an output signal from a sensor which detects the collision of a vehicle, and the generated combustion gas is ejected into the air bag through a plurality of gas ejecting bores provided in a peripheral wall of the casing.
With a gas generator using only the combustion gas as in such gas generator, however, it is necessary to mount a cooler for cooling a high temperature generated combustion gas and a filter for removing a solid residue or cinder of the gas-generating agent contained in the combustion gas. This causes a problem that the structure of the gas generator is complicated, resulting an increase in cost.
Thereupon, a gas generator has been proposed which includes a compressed gas previously filled in the casing for expanding the air bag, and a small amount of gas-generating agent incorporated in the casing (for example, Japanese Patent Publication No. 578/79). With such gas generator, the gas-generating agent is ignited and fired on the basis of an output signal from a collision sensor, and at the same time, an end of the casing is cleaved by a detonator, thereby permitting the compressed gas and the combustion gas from the gas-generating agent to be mixed with each other and ejected in the form of the mixture. If the compressed gas and the combustion gas are used in combination in this manner, the compressed gas is heated moderately by mixing of the compressed gas with the high temperature combustion gas and hence, a reduction in temperature due to an adiabatic expansion of the compressed gas upon ejection thereof from the casing can be compensated for, thereby avoiding the loss of gas volume, but also the gas-generating agent may be of a small amount and for this reason, the need for the cooler and the filter can be eliminated, leading to a simplified structure.
In the gas generator using the combustion gas and the compressed gas in combination, as described above, the detonator is provided at the end of the casing for cleaving the gas ejecting bores, and moreover, the compressed gas and the combustion gas are ejected from only the end of the casing. Therefore, there is a problem that if no gas diffusing member such as a baffle plate is provided opposed to the gas ejecting bores, the gas cannot be supplied equally into the air bag.